Compact orthopedic anti-rotation device

ABSTRACT

Embodiments of the present invention relate to systems, methods, and apparatus for immobilizing and/or securing bone portions. Particularly, at least one embodiment involves a compact anti-rotation device that can secure adjacent bones and/or bone portions in a manner that prevents or limits relative rotational movement thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser.No. 13/741,263, filed Jan. 14, 2013, which claims the benefit of andpriority to U.S. Provisional Patent Application No. 61/586,075, filedJan. 12, 2012, entitled “Inline, Multi-Tine Staple For OrthopedicSurgical Applications,” the entire contents of which are incorporatedherein by this reference.

BACKGROUND OF THE INVENTION 1. The Field of the Invention

This invention relates to systems, methods, and apparatus for securingbone portions.

2. Background and Relevant Art

Various injuries and/or age-related conditions can affect bones,ligaments, and joint health in a manner that may require medicalintervention. For instance, an injury to a ligament can result inseparation or dissociation of bones previously connected by a ligament.Among other things, such injuries can lead to loss of mobility as wellas discomfort or pain. Therefore, it is commonly desirable to repairdamaged ligaments and to realign the bones into normal (e.g.,pre-injury) anatomical positions.

For example, tear of scapholunate interosseous ligament (“SLIL”), whichconnects the scaphoid and lunate bones of the wrist, can affect thepatient's wrist movement and mobility. In some instances, the SLIL canbe repaired with surgery (e.g., by reconnecting the scaphoid and lunatebones). To heal properly, however, the scaphoid and lunate bones mayhave to remain substantially immobilized relative to each other.

Commonly used devices and methods for immobilizing the scaphoid andlunate bones are imperfect. Specifically, a patient's ordinary wristmovements normally rotate the scaphoid and lunate bones relative to eachother. Hence, typical devices for restricting such rotation experiencetorque applied thereon by the movement of the patient's wrist. In someinstances, such devices cannot fully absorb the applied torque and,thus, permit rotation of the scaphoid and lunate bones. As mentionedabove, rotation of the scaphoid and lunate bones can interfere with thehealing of the repaired ligament and can result in further injury.

Accordingly, there are a number of disadvantages in current devices andmethods used for immobilizing relative movement and/or rotation of bonesthat can be addressed.

BRIEF SUMMARY

Embodiments of the present invention provide systems, methods, andapparatus for immobilizing and/or securing bone portions. Particularly,at least one embodiment involves a compact anti-rotation device that cansecure adjacent bones and/or bone portions in a manner that prevents orlimits relative rotational movement thereof. Accordingly, the compactanti-rotation device can help promote healing of reconnected boneportions, which may require maintaining the bone portions substantiallyimmobilized relative to each other.

In one embodiment, a compact anti-rotation device for securing adjacentbones and preventing or impeding such bones from relative rotationthereof, to facilitate healing of the bones or tissue or ligamentsconnected thereto is described. The device includes a torsion bar havinga first end and a second end. The torsion bar is sized and configured totwist and deform in response to a torque applied thereto. The deviceincludes a first anchoring member coupled to or integrated with thefirst end of the torsion bar and a second anchoring member coupled to orintegrated with the second end of the torsion bar. Each of the firstanchoring member and the second anchoring member has a plurality ofprongs oriented substantially perpendicularly to the torsion bar.

In some embodiments, each prong of the plurality of prongs issubstantially parallel to other prongs of the plurality of prongs. Acenter axis of each prong of the plurality of prongs, in furtherembodiments, is approximately aligned with and perpendicular to alongitudinal axis of the torsion bar.

At least one prong of the plurality of prongs of the first anchoringmember, in some embodiments, has a piercing tip located near or forminga distal end thereof. In further embodiments, each prong of theplurality of prongs has a piercing tip located near or forming a distalend thereof.

In some embodiments, each prong of the plurality of prongs has ablade-like configuration. Each of the first and second anchoringmembers, in further embodiments, comprises two prongs.

In another embodiment, a system for securing adjacent bones andpreventing such bones from relative rotation, to facilitate healing ofthe bones or tissue or ligaments connected thereto is described. Thesystem includes one or more elongated inner connectors sized andconfigured to be embedded in the adjacent bones. The one or moreelongated inner connectors are further sized and configured to guide andorient the adjacent bones relative to each other. The system includes acompact anti-rotation device. The compact anti-rotation device includesat least one torsion bar having a substantially linear shape, a firstanchoring member coupled to or integrated with the at least one torsionbar, and a second anchoring member coupled to or integrated with the atleast one torsion bar, wherein the first and second anchoring memberscomprise a plurality of prongs.

In some embodiments, each prong of the plurality of prongs is orientedsubstantially perpendicular to the at least one torsion bar. Theplurality of prongs, in further embodiments, are positioned in line withone another.

A center axis of each prong of the plurality of prongs, in someembodiments, is approximately aligned with and perpendicular to alongitudinal axis of the at least one torsion bar. In furtherembodiments, the one or more elongated inner connectors comprise a firstK-wire and a second K-wire.

In some embodiments, the one or more elongated inner connectors comprisea bone screw. The adjacent bone portions, in further embodiments,comprise a scaphoid bone and a lunate bone.

In another embodiment, a method of immobilizing and securing adjacentbones and preventing such bones from relative rotation, to facilitatehealing of the bones or tissue or ligaments connected thereto isdescribed. The method includes positioning a first bone and a second,adjacent bone at desired locations relative to each other. At least oneelongated inner connector is inserted through the first bone and throughthe second bone, thereby fixing the desired location of the first andsecond bones relative to each other. A first anchor of a compactanti-rotation device is inserted through a first outer surface of thefirst bone and into the first bone. A second anchor of the compactanti-rotation device is inserted through a second outer surface of thesecond bone and into the second bone.

In some embodiments, the first bone comprises a scaphoid bone and thesecond bone comprises a lunate bone. Inserting the at least oneelongated inner connector through the first bone and through the secondbone, in further embodiments, includes inserting a first K-wire and asecond K-wire through the scaphoid and lunate bones.

Inserting the first anchor of a compact anti-rotation device through afirst outer surface of the first bone and into the first bone, in someembodiments, comprises inserting a first plurality of prongs that definethe first anchor into the scaphoid bone. In further embodiments, thefirst plurality of prongs are inserted at an angle substantiallyperpendicular to an axis of rotation of a joint defined by the scaphoidand lunate bones. In yet further embodiments, inserting the secondanchor of the compact anti-rotation device through a second outersurface of the second bone and into the second bone comprises insertinga second plurality of prongs that define the second anchor into thelunate bone.

Additional features and advantages of exemplary embodiments of theinvention will be set forth in the description which follows, and inpart will be obvious from the description, or may be learned by thepractice of such exemplary embodiments. The features and advantages ofsuch embodiments may be realized and obtained by means of theinstruments and combinations particularly pointed out in the appendedclaims. These and other features will become more fully apparent fromthe following description and appended claims, or may be learned by thepractice of such exemplary embodiments as set forth hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features of the invention can be obtained, a moreparticular description of the invention briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. For better understanding, the likeelements have been designated by like reference numbers throughout thevarious accompanying figures. Understanding that these drawings depictonly typical embodiments of the invention and are not therefore to beconsidered to be limiting of its scope, the invention will be describedand explained with additional specificity and detail through the use ofthe accompanying drawings in which:

FIG. 1A illustrates a side view of an immobilization system deployed inscaphoid and lunate bones in accordance with one embodiment of thepresent invention;

FIG. 1B illustrates a side view of an immobilization system deployed inscaphoid and lunate bones in accordance with another embodiment of thepresent invention;

FIG. 2 illustrates a perspective view of a simple staple with bent ortwisted opposing prongs;

FIG. 3 illustrates a perspective view of a twisted compact anti-rotationdevice in accordance with one embodiment of the present invention;

FIG. 4 illustrates a side view of an compact anti-rotation device inaccordance with one embodiment of the present invention;

FIG. 5 illustrates a perspective view of an compact anti-rotation devicein accordance with another embodiment of the present invention;

FIG. 6 illustrates a chart of acts for a method of immobilizing adjacentbones or bone portions in accordance with one embodiment of the presentinvention;

FIG. 7 illustrates a perspective view of a test setup used inexperiments performed in connection with the present invention; and

FIG. 8 illustrates side views of scaphoid and lunate bone pairs andimmobilization devices and/or systems used in experiments performed inconnection with the present invention.

DETAILED DESCRIPTION

Embodiments of the present invention provide systems, methods, andapparatus for immobilizing and/or securing bone portions. Particularly,at least one embodiment involves a compact anti-rotation device that cansecure adjacent bones and/or bone portions in a manner that prevents orlimits relative rotational and bending movement thereof. Accordingly,the compact anti-rotation device can help promote healing of reconnectedbone portions, which may require maintaining the bone portions in asubstantially immobilized state relative to each other. For example, thebone portions may be restricted from moving relative to each other, suchthat some slight movement is allowed, but any major movement isprevented.

In one example, the compact anti-rotation device can include a torsionbar and anchoring members on opposing sides thereof. Such anchoringmembers can be secured to the bone portions, thereby immobilizing thebone portion and preventing or limiting rotation of the bone portionsrelative to each other. For instance, the compact anti-rotation devicecan have a first anchoring member coupled to or integrated with a firstend of the torsion bar and a second anchoring member coupled to orintegrated with a second end of the torsion bar. As further describedbelow, insufficient anchoring of the torsion bar can lead to bending ortwisting of the anchoring members relative to the torsion bar instead oftorquing or twisting the torsion bar.

In one embodiment, the anchoring members can be inserted or embeddedinto the bone portions. Moreover, the anchoring members can beconfigured in a manner that the anchoring members can resist rotationwithin the bone portions. For example, each anchoring member cancomprise multiple prongs protruding from the torsion bar of the compactanti-rotation device. Multiple prongs can resist or prevent rotation ofthe anchoring members within the bone portions, as further describedbelow. In some embodiments, the prongs can be inserted through an outersurface of the bone portions, such that the torsion bar remains outsideof the bone portions.

Embodiments also include an immobilization system that can be employedfor securing adjacent bone portions. Such a system or kit canincorporate one or more elongated inner connectors (e.g., K-wires,screws, etc.) that can be placed or embedded within the bone portions.The system also can include the compact anti-rotation device, portionsof which can be embedded inside the bone portions, through an outersurface thereof. As such, the elongated inner connectors can connect andlocate the bone portions in anatomically correct or desirable positionsrelative to each other and can at least partially restrict relativelateral and/or rotational movement of the bone portions. The compactanti-rotation device can further reinforce the connection between thebone portions and can provide sufficient immobilization therebetween tofacilitate healing (e.g., healing of a repaired ligament between thebone portions).

In one embodiment, the immobilization system and/or device can be usedto repair scapholunate joint. In particular, the immobilization systemand/or device can be used to secure and or immobilize scaphoid andlunate bones (e.g., after repairing the scapholunate ligament). Asmentioned above, such immobilization can sufficiently restrain thescaphoid and lunate bones from rotating relative to each other, whichcan facilitate healing of the repaired ligament.

FIGS. 1A-1B illustrate exemplary deployments of compact anti-rotationdevices and systems. Specifically, FIG. 1A illustrates the scaphoid bone10 and the lunate bone 20 secured together by an immobilization system100. For instance, the immobilization system 100 can include one or moreelongated internal connectors 110 (e.g., K-wires 110 a, 110 b). Theimmobilization system 100 also can include a compact anti-rotationdevice 120, which can further secure the scaphoid bone 10 and the lunatebone 20 together.

Particularly, the compact anti-rotation device 120 can aid in preventingthe scaphoid bone 10 and the lunate bone 20 from rotating relative toeach other. Relative rotation (and/or other relative movement) of thescaphoid bone 10 and the lunate bone 20 can disrupt a newly repairedligament. Accordingly, providing sufficient immobilization of thescaphoid bone 10 and the lunate bone 20 can improve healing of therepaired ligament.

More specifically, as the patient rotates a wrist that has the recentlyrepaired scaphoid bone 10 and the lunate bone 20, a torque T can beapplied to the scapholunate joint 30, which typically tends to rotatethe scaphoid bone 10 and the lunate bone 20 relative to each other. Forinstance, a 50° rotation of the wrist can result in approximately 10°differential rotation of the scaphoid bone 10 and the lunate bone 20. Asnoted above, the torque T can result in relative rotation of thescaphoid bone 10 and the lunate bone 20, which may disrupt the healingprocess of a recently repaired scapholunate ligament. Hence, in one ormore embodiments, the immobilization system 100 can sufficientlycounteract the torque T to prevent or limit such rotation. For instance,in one or more embodiments, the immobilization system 100 can limit suchrotation of the scaphoid bone 10 relative to the lunate bone 20 to lessthan 10°, 5°, 2°, or 0.5°. In one example, the immobilization system 100can prevent or limit relative rotation of scaphoid and lunate bones 10,20 to less than about 1° in response to an applied torque ofapproximately 200 N-mm.

In some embodiments, the compact anti-rotation device 120 can comprise atorsion bar 130 and opposing anchoring members 140 a, 140 b that cancouple the torsion bar 130 to the scaphoid bone 10 and the lunate bone20, respectively, thereby securing the scaphoid bone 10 and the lunatebone 20 together. In at least one embodiment, the anchoring member 140 aand/or the anchoring member 140 b can be configured to prevent rotationthereof inside the respective scaphoid bone 10 and the lunate bone 20.It should be appreciated that, as described in more detail below inconnection with experimental data, commonly used devices can be prone torotation within the scaphoid bone 10 and the lunate bone 20 when torqueperpendicular to the scapholunate joint 30 is applied thereto.Accordingly, at least one embodiment of the present invention providesfor limiting or preventing rotation of the anchoring members 140 a, 140b, which can improve efficacy of the compact anti-rotation device 120 inlimiting or preventing rotation of the scaphoid bone 10 and the lunatebone 20 relative to each other.

In some embodiments, the anchoring members 140 a, 140 b can havemultiple prongs that can be inserted into the scaphoid bone 10 and thelunate bone 20, respectively. The multiple prongs can limit or eliminaterotation of the anchoring members 140 a, 140 b within the bones, asrespective axes of the prongs can be separated by a distance. As such,the prongs can resist rotating within the scaphoid and lunate bones 10,20.

Therefore, as the anchoring members 140 a, 140 b can remainsubstantially fixed relative to the respective scaphoid bone 10 and thelunate bone 20, the anchoring members 140 a, 140 b can apply torque ontothe torsion bar 130, as the scaphoid and lunate bones 10, 20 attempt torotate relative to each other. As the torque is applied, the torsion bar130 can twist, thereby deforming substantially along the entire lengththereof. In some embodiments, such deformation can be elastic, such thatthe torsion bar 130 can return substantially to its un-deformedconfiguration after the torque is removed (e.g., after the scaphoid bone10 and the lunate bone 20 are rotated back to their original relativepositions). Alternatively, the torsion bar 130 can plastically deform inresponse to the applied torque, thereby maintaining the deformedconfiguration after the torque is removed.

It should be appreciated that whether the torsion bar 130 experiences anelastic or plastic deformation can vary from one embodiment to another.Moreover, in some instances the torsion bar 130 can elastically deformin response to a twist to a predetermined first angle. The same torsionbar 130 also can plastically deform in response to a twist to anotherangle, which is greater than the first angle.

In light of this disclosure it should be appreciated that joints, whichcan be secured by the compact anti-rotation device 120, can be understress or strain in response to ordinary movements of the patient. Forinstance, the scapholunate joint 30 can be placed under strain inmultiple planes during ordinary movement of the patient's wrist. Inother words, as mentioned above, the scaphoid bone 10 and the lunatebone 20 can rotate relative to each other, which can place thescapholunate joint 30 under strain. Furthermore, the scaphoid and lunatebones 10, 20 typically have small surface areas, which contribute todifficulty of securing the scaphoid bone 10 relative to the lunate bone20 in a manner that can prevent relative rotation thereof and facilitatehealing.

Accordingly, at least one embodiment of the compact anti-rotation device120 can be sufficiently small or compact as well as resilient tofacilitate attachment thereof to the scaphoid and lunate bones 10, 20and to prevent or impede relative rotation of thereof. Hence, in atleast one embodiment, the anchoring members 140 a, 140 b can besufficiently small or compact as to securely couple to the scaphoid bone10 and the lunate bone 20, respectively. Likewise, the torsion bar 130can be sufficiently compact such as to facilitate attachment of thecompact anti-rotation device 120 to the scaphoid and lunate bones 10,20.

In light of this disclosure, it should be appreciated that “compactness”referenced herein is a measure that is relative to the size of thescaphoid and lunate bones 10, 20 as well as to generally available spacein the region of the patient's wrist. For example, the compactanti-rotation device 120 can have a length in the range of 10 mm to 13mm, 11 mm to 18 mm, 15 mm to 20 mm, and 19 mm to 25 mm. Preferably, thelength of the compact anti-rotation device 120 can be about 22 mm. Insome embodiments, the length of the compact anti-rotation device 120 canbe greater than 25 mm or less than 10 mm. The compact anti-rotationdevice 120 also can have a thickness in the range of 1 mm to 5 mm, 3 mmto 8 mm, and 7 mm to 10 mm. In one or more embodiments, however, thethickness of the compact anti-rotation device 120 can be greater than 10mm or less than 1 mm.

In some embodiments, at least a portion of the anchoring members 140 a,140 b can be inserted into the scaphoid bone 10 and the lunate bone 20,respectively. Accordingly, the compact anti-rotation device 120 can havea third dimension that can relate to the width thereof or to the maximumdepth of penetration of the anchoring members 140 a, 140 b into thebone. Particular width of the compact anti-rotation device 120 can varyfrom one embodiment to another and can depend on location or position ofthe elongated internal connectors 110, such that the anchoring members140 a, 140 b do not hit and/or damage the elongated internal connectors110.

In one example, as described above, the elongated internal connectors110 can comprise the K-wires 110 a, 110 b, which can have suitablediameters and lengths. For instance, the K-wires 110 a, 110 b can bestandard-sized K-wires (e.g., 0.045″ or 1.1 mm diameter). Moreover,spacing between the K-wires 110 a, 110 b also can vary from oneembodiment to another. Embodiments of the present invention can includeK-wires 110 a, 110 b having a spacing therebetween in the range ofapproximately 1 mm to 3 mm and 2 mm to 5 mm. In some embodiments, thespacing between the K-wires 110 a, 110 b can be greater than 5 mm orless than 1 mm. Specifically, among other considerations, the spacingbetween the K-wires 110 a, 110 b can depend upon the particular size andshape of the patient's scaphoid bone 10 and the lunate bone 20 as wellas on the size of the K-wires 110 a, 110 b.

In any event, the K-wires 110 a, 110 b can locate and orient thescaphoid bone 10 and the lunate bone 20 relative to each other as wellas at least partially immobilize the scaphoid and lunate bones 10, 20from relative rotational movement. It should be appreciated that thegreater the spacing between the K-wires 110 a, 110 b, the greater theresistance that can be provided to relative rotation of the scaphoidbone 10 and the lunate bone 20 (as discussed below in connection withexperimental data). Increased spacing between the K-wires 110 a, 110 balso can limit the maximum possible depth of penetration by theanchoring members 140 a, 140 b into the respective scaphoid and lunatebones 10, 20, which can limit the maximum width of the compactanti-rotation device 120.

Some embodiments can include an elongated internal connector that canfasten the scaphoid bone 10 and the lunate bone 20 together in a securemanner. For example, FIG. 1B illustrates an immobilization system 100 a,which includes an elongated internal connector that is a bone screw 110c. The immobilization system 100 a and all of the components andelements thereof can be similar to or the same as the immobilizationsystem 100 (FIG. 1A) and all of its respective components and elements,except as otherwise described herein. The bone screw 110 c can securelycouple together the scaphoid bone 10 and the lunate bone 20.

For instance, the bone screw 110 c can be blind or an un-cannulatedscrew. Alternatively, the bone screw 110 c can be a cannulated screw.Thus, in one or more embodiments, the cannulated bone screw 110 c canslide over a K-wire, positioned inside the scaphoid bone 10 and/orinside the lunate bone 20. As such, the scaphoid and lunate bones 10, 20can be placed into correct orientation, positions, and alignmentrelative to each other before the scaphoid bone 10 and the lunate bone20 are secured together with the bone screw 110 c.

In some instances, the bone screw 110 c can provide greater resistanceto decoupling or dissociation of the scaphoid and lunate bones 10, 20from each other, as compared with the K-wires 110 a, 110 b (FIG. 1A). Atthe same time, however, as described below in experimental results, thebone screw 110 c may provide less resistance to relative rotation of thescaphoid and lunate bones 10, 20 as compared with the K-wires 110 a, 110b (FIG. 1A).

Additionally, in some embodiments, the bone screw 110 c can allow for acompact anti-rotation device 120 a with anchoring members 140 a′, 140 b′that can be longer than the anchoring members 140 a, 140 b of thecompact anti-rotation device 120, as can be used in conjunction with theK-wires 110 a, 110 b of the immobilization system 100 (FIG. 1A).Accordingly, for instance, the compact anti-rotation device 120 a alsocan incorporate a torsion bar 130 a with a greater cross-sectional areathan the torsion bar 130 of the compact anti-rotation device 120 (FIG.1A). In other words, the larger anchoring members 140 a′, 140 b′ canwithstand greater torque without rotating within the scaphoid and lunatebones 10, 20. As such, the anchoring members 140 a′, 140 b′ also cantransfer more torque onto the torsion bar 130 a; because the torsion bar130 a can be larger than the torsion bar 130 (FIG. 1A), the torsion bar130 a also can absorb and withstand a greater amount of torque Ttransferred thereto. Therefore, in at least one embodiment, the compactanti-rotation device 120 a can be configured to provide sufficientanti-rotational reinforcement in the immobilization system 100 a thatincorporates the bone screw 110 c.

In any event, as described above, the anchoring members 140 a′, 140 b′can be coupled to and/or inserted into the respective scaphoid andlunate bones 10, 20 in a manner that allows the anchoring members 140a′, 140 b′ to transfer torque T to the torsion bar 130 a, therebypreventing or impeding relative rotation of the scaphoid and lunatebones 10, 20. By contrast, it should be appreciated that some anchoringmembers may be insufficiently secured within the scaphoid bone 10 and/orwithin the lunate bone 20. For example, FIG. 2 illustrates a standardstaple 200 having opposing prongs 210, 220. The prongs 210, 220 can becoupled to or integrated with a connector or torsion bar 230.

As described below in the experimental results, the prongs 210, 220 ofthe staple 200 can rotate within the adjacent bones (e.g., within thescaphoid and lunate bones), for instance, when a torque is applied abouta joint comprising such bones. In particular, rotation of the prongs210, 220 within the scaphoid and lunate bones can prevent the prongs210, 220 from transferring torque from the bones to the torsion bar 230.Consequently, instead of twisting the torsion bar 230, the toquetransferred to the staple 200 can bend the prongs 210, 220 relative tothe torsion bar 230 (e.g., at locations 240 a, 240 b). As such, thestaple 200 can absorb less torque as compared with the compactanti-rotation device 120, 120 a (FIGS. 1A, 1B) of the present invention.

In contrast to the staple 200, at least one embodiment of the presentinvention, as illustrated in FIG. 3, can incorporate the anchoringmembers 140 a, 140 b of the compact anti-rotation device 120, which cantransfer torque applied to the scaphoid and lunate bones to the torsionbar 130. Accordingly, the torsion bar 130 can absorb more energy (ascompared with the torsion bar 230 of the staple 200; FIG. 2), becausethe anchoring members 140 a, 140 b can remain substantially fixed withinthe scaphoid and lunate bones and, thus, can transfer the torque appliedat the scapholunate joint to the torsion bar 130. Therefore, (assupported by experimental data provided below), the compactanti-rotation device 120 can provide a substantially greateranti-rotational resistance to the scaphoid and lunate bones (e.g., ascompared with the standard staple 200).

As noted above, the anchoring members 140 a, 140 b can be configured tobe inserted into the scaphoid and lunate bones of the scapholunatejoint. For instance, as illustrated in FIG. 4, the anchoring members 140a, 140 b of the compact anti-rotation device 120 can comprise prongs 150a, 150 b, 150 c, 150 d. More specifically, in some embodiments, theanchoring member 140 a can comprise prongs 150 a, 150 b, and theanchoring member 140 b can comprise prongs 150 c, 150 d. As mentionedabove, the prongs 150 a, 150 b, 150 c, 150 d can be embedded into andsecured within opposing bones, such as the scaphoid and lunate bones.

Thus, in at least one embodiment, distal ends of the prongs 150 a, 150b, 150 c, 150 d can have piercing tips 160. In some instances, thecompact anti-rotation device 120 can be implanted with an automatedtool. Hence, the 160 can penetrate into the bone. Additionally oralternatively, holes corresponding with the prongs 150 a, 150 b, 150 c,150 d can be predrilled in the bones and the prongs 150 a, 150 b, 150 c,150 d of the compact anti-rotation device 120 can be inserted or tappedinto those holes. Consequently, in some embodiments, the distal ends ofthe prongs 150 a, 150 b, 150 c, 150 d can have any number of othersuitable configurations which may or may not be the piercing tips 160.

Furthermore, at least one embodiment can include the prongs 150 a, 150b, 150 c, 150 d that incorporate bars, spikes, or other protrusions thatcan aid in securing the prongs 150 a, 150 b, 150 c, 150 d within thebone. For instance, tapered barbs can be disposed along the lengths ofeach of the prongs 150 a, 150 b, 150 c, 150 d. Alternatively, the prongs150 a, 150 b, 150 c, 150 d can be substantially flat or straight and canhave a substantially smooth surface.

Additionally, the prongs 150 a, 150 b, 150 c, 150 d have a substantiallyorthogonal orientation with respect to the torsion bar 130. Moreover, inone or more embodiments, the prongs 150 a, 150 b, 150 c, 150 d also canbe substantially parallel relative to each other. Accordingly, parallelorientation of the prongs 150 a, 150 b, 150 c, 150 d can allow thecompact anti-rotation device 120 to be inserted in a single,substantially linear movement. Furthermore, the prongs 150 a, 150 b, 150c, 150 d can be positioned substantially in the same line as one anotheras well as concentrically with respect to a longitudinal axis extendingthrough the torsion bar 130. Concentric positioning of the prongs 150 a,150 b, 150 c, 150 d with the torsion bar 130 can optimize transmittal oftorque from the prongs 150 a, 150 b, 150 c, 150 d onto the torsion bar130.

Also, it should be noted that perpendicular orientation of the prongs150 a, 150 b, 150 c, 150 d relative to the torsion bar 130 canfacilitate placement of the compact anti-rotation device 120 in a mannerthat the torsion bar 130 remains outside of the scaphoid and lunatebones, while the prongs 150 a, 150 b, 150 c, 150 d are embedded insideof the bones. In other words, positioning the torsion bar 130approximately parallel to the axis of rotation (as shown and describedin connection with FIG. 7 below) at the scapholunate joint can be easierthan for differently configured devices. Specifically, a user can orientthe prongs 150 a, 150 b, 150 c, 150 d approximately perpendicular to theaxis of rotation and can thereafter deploy the compact anti-rotationdevice 120.

In one embodiment, holes for accommodating the prongs 150 a, 150 b, 150c, 150 d can be predrilled at approximately the same angles andapproximately perpendicular to the axis of rotation. Without measuringtools and/or supplemental equipment, positioning the prongs 150 a, 150b, 150 c, 150 d and/or drilling the holes in the bones at approximatelyorthogonal orientation can be easier than performing the same acts atother (i.e., acute or obtuse) angles. That is, non-orthogonal angles canbe difficult and/or impractical or impossible to estimate withsufficient accuracy and can increase the degree of difficulty indeploying the anti-rotation device.

As described above, the width of the compact anti-rotation device 120can vary from one embodiment to another and can depend, among otherthings, on the length of the prongs 150 a, 150 b, 150 c, 150 d. Forexample, the length of the prongs 150 a, 150 b, 150 c, 150 d can be inthe range of 5 mm to 8 mm, 7 mm to 10 mm, and 9 mm to 15 mm. Preferably,the length of the prongs can be about 10 mm. It should be appreciated,however, that, in some embodiments, the length of the prongs 150 a, 150b, 150 c, 150 d can be less than 5 mm or greater than 10 mm.

The prongs 150 a, 150 b, 150 c, 150 d of the compact anti-rotationdevice 120 also can have any number of suitable distances therebetween.In one embodiment, spaces between the prongs 150 a, 150 b and the spacesbetween the prongs 150 c, 150 d can be substantially the same. Forinstance, the prongs 150 a, 150 b can be spaced at approximately 1.8 mm.Other embodiments can include spaces between the prongs 150 a and 150 bthat are greater or less than 1.8 mm.

In at least one embodiment, the compact anti-rotation device 120 alsocan have transition radii between the torsion bar 130 and the prongs 150a, 150 b, 150 c, 150 d. Specifically, the compact anti-rotation device120 can include transition radii 170 a, 170 b, 170 c between the torsionbar 130 and the prongs 150 a, 150 b. Similarly, the compactanti-rotation device 120 can have transition radii 170 d, 170 e, 170 fbetween the torsion bar 130 and the prongs 150 c, 150 d. The transitionradii 170 a, 170 b, 170 c, 170 d, 170 e, 170 f can help reduce thestress at the transition or connection point between the torsion bar 130and the prongs 150 a, 150 b, 150 c, 150 d. Accordingly, the transitionradii 170 a, 170 b, 170 c, 170 d, 170 e, 170 f can increase the strengthof the compact anti-rotation device 120 as well as the maximum amount oftorque that the anchoring members 140 a, 140 b can transfer to thetorsion bar 130.

Although the above embodiments describe the compact anti-rotation device120 as having two prongs one each end thereof, it is to be appreciatedthat this invention is not so limited. Particularly, the anchoringmembers of the compact anti-rotation device can have more than twoprongs, which can vary from one embodiment to the next. In at least oneembodiment, the compact anti-rotation device can have three, four, or agreater number of prongs one any one end thereof. Moreover, as describedbelow, the prongs can have any number of suitable shapes andconfigurations, such as to form the anchoring members of the compactanti-rotation device, which can remains substantially fixed within thebone.

The compact anti-rotation device 120 also can comprise any number ofsuitable materials, composites, or combinations thereof. In oneembodiment, the compact anti-rotation device 120 can comprise a Nickeltitanium alloy (also known as Nitinol®). Additionally or alternatively,the compact anti-rotation device 120 can comprise any suitablebiodegradable, bioresorbable, or bioabsorbable material. For example, atleast a portion of the compact anti-rotation device 120 may be made ofpoly-L-lactic acid, PLLA (polylactic acid), PGA (polyglycolic acid), acopolymer such as PLLA-PGA, other biodegradable, bioresorbable, orbioabsorbable materials, or combinations and/or composites thereof.Furthermore, the compact anti-rotation device 120 can comprise multiplematerials, which can be coupled or fused together to from the compactanti-rotation device 120. In one example, the torsion bar 130 may beformed of one material and the anchoring members 140 a, 140 b may beformed of another material. For instance, the torsion bar 130 may beformed of a biodegradable, bioresorbable, or bioabsorbable materialwhile the anchoring members may be formed of a Nickel titanium alloy.Also, the compact anti-rotation device 120 can be coated with abeneficial agent (e.g., anti-inflammatory, antibacterial, etc.), such asagents that can promote bone adhesion to the implant, includinghydroxyapitite, as well as agents to strengthen bone such as bonemorphogenic proteins, or statins, other beneficial agents, orcombinations thereof.

Resistance to deformation of the compact anti-rotation device can beincreased by increasing the strength of the torsion bar 130 (e.g., byincreasing the size or material thereof) and/or by increasing resistanceof the anchoring members to rotation within the bone. For instance, asillustrated in FIG. 5, a compact anti-rotation device 120 b can includeanchoring members 140 a″, 140 b″ coupled to or integrated with a torsionbar 130 b. Except as otherwise described herein, the compactanti-rotation device 120 b and all of its components and elements can besimilar to or the same as the compact anti-rotation devices 120, 120 a(FIGS. 1A, 1B, 3) and all of their respective components and elements.

In one example, the compact anti-rotation device 120 b can haveblade-like prongs 150 a″, 150 b″, 150 c″, 150 d″. In particular, theblade-like prongs 150 a″, 150 b″, 150 c″, 150 d″ can have widths greaterthan thicknesses thereof. As such, the blade-like prongs 150 a″, 150 b″,150 c″, 150 d″ can provide additional resistance to rotation within thebone and can transfer greater amount of torque to the torsion bar 130 b.

Consequently, the compact anti-rotation device 120 b also canincorporate the torsion bar 130 b that has a higher strength than, forexample, the torsion bar 130 (FIG. 1A). In some instance, deployment ofthe compact anti-rotation device 120 b can be limited by the geometry ofthe bones as well as available in the area surrounding the bones.Accordingly, the compact anti-rotation device 120 b can be deployed inbones and locations that provide sufficient space therefor.

Furthermore, embodiments of the present invention can include prongs ofany number of configurations and shapes. For instance, the prongs canhave a substantially cylindrical shape. Additionally or alternatively,in some embodiments, the prongs also can have a tubular shape.

FIGS. 1A-1B and 3-5, and the corresponding text, provide a number ofdifferent components and mechanisms for securing and immobilizingadjacent bones (e.g., the scaphoid and lunate bones). In addition to theforegoing, embodiments of the present invention also can be described interms of one or more acts in a method for accomplishing a particularresult. For example, FIG. 6 illustrates a flowchart of one exemplarymethod for securing and immobilizing adjacent bones or bone portionsrelative to each other. The acts of FIG. 6 are described below withreference to the components of FIGS. 1A-1B and 3-5.

For example, FIG. 6 shows that one embodiment of the method of securingand immobilizing adjacent bones or bone portions can include an act 300of positioning first and second bone portions at desired locations. Inone embodiment, the first and second bone portions can comprise thescaphoid bone 10 and the lunate bone 20, respectively. For instance, thescaphoid bone 10 and the lunate bone 20 can be positioned at theirrespective normal (or pre-injury) anatomical locations.

The method also can include an act 310 of inserting the elongatedinternal connector 110 through the first and second bone portions. Asnoted above, at least some embodiments of the present invention also caninclude inserting multiple elongated internal connectors 110. Hence, forexample, the act 310 can involve inserting the K-wires 110 a, 110 b.Additionally or alternatively, the act 310 can involve inserting thebone screw 110 c. The elongated internal connector(s) 110 can align andorient the bone portions, such as the scaphoid bone 10 and the lunatebone 20, relative to each other. Furthermore, the elongated internalconnector(s) 110 also can at least partially restrain and/or immobilizethe bone portions from relative movement and/or rotation.

In addition, the method can include an act 320 of inserting first andsecond anchoring members (e.g., anchoring members 140 a, 140 b, 140 a′,140 b′, 140 a″, 140 b″) of the compact anti-rotation device 120, 120 a,120 b into the respective first and second bone portions, such as intothe scaphoid bone 10 and the lunate bone 20. The anchoring members ofthe compact anti-rotation device 120, 120 a, 120 b can prevent or impederelative rotation of the scaphoid and lunate bones 10, 20. Accordingly,inserting or installing the elongated internal connector(s) 110 (e.g.,K-wires 110 a, 110 b and/or bone screw 110 c) as well as the compactanti-rotation device 120, 120 a, 120 b can help to immobilize thescaphoid bone 10 and the lunate bone 20, thereby facilitating healingthereof.

Experimental Data

Multiple specimens of scaphoid and lunate bone were tested.Specifically, the scaphoid and lunate bones were individually potted inaluminum cylinders using polymethlmethacrylate (PMMA). In preparationfor potting, two perpendicular K-wires were placed in the most distalaspect of each scaphoid and lunate bones in a plane parallel to thescapholunate joint. These K-wires were only used to help anchor thespecimen in the fixation pots and were not part of the scapholunatefixation hardware. Care was taken to ensure that these K-wires did notadd to or interfere with the stability of the scapholunate fixation.Prior to potting, any exposed implant metal from the scapholunatefixation was covered with clay to prevent incorporation into the PMMA.The scaphoid bone was placed in a custom fabricated aluminum pot andheld in place by four perpendicularly oriented screws. PMMA was thenadded to the pot and allowed to cure. The process was then repeated tosecure the lunate bone in a separate custom aluminum pot.

A bi-axial materials testing machine (MTS, Eden Prairie, Minn.) was usedto test each scapholunate construct. As illustrated in FIG. 7, thepotted scaphoid and lunate bones were secured in the testing machine andoriented in such a way as to allow the application of torque to theconstruct about an axis perpendicular to the scapholunate joint andapproximately parallel to the centrally directed screw or K-wirefixation devices. Angular displacement was chosen as the controlvariable for testing with the resulting torque used as the primaryoutcome measure. Data was continuously collected at a rate of 100samples per second. Axial compression across the joint was held constantat approximately zero, allowing the scapholunate joint to distract orcompress freely in response to the torsional load. The potted lunatebone was rotated relative to the independently potted scaphoid bone.Torque was applied in a clockwise direction on the left hand specimensand in a counter-clockwise direction on the right hand specimens, aboutan axis perpendicular to the scapholunate joint, so as to cause thescaphoid bone to flex relative to the lunate bone. An X-Y table mountedin line with the axis of rotation allowed for substantiallyunconstrained motion of the scaphoid bone relative to the lunate bone inany direction perpendicular to the axis of rotation. Each specimen wasrotated to 50 degrees, which is the failure point of the nativescapholunate interosseous ligament (“SLIL”) according to publishedliterature. Statistical analysis of the data was done using ANOVA(Statistica) followed by Fisher LSD for comparisons. Significance wasset at p=0.05.

The compact anti-rotation device as well as a standard staple were usedin the experiments. The standard staple refers to a standard 13×10 mmstaple. The compact anti-rotation device was prepared by welding twostandard (13×10 mm) staples to form a 22×10 mm compact anti-rotationdevice, having 1.8 mm separation between the outer prongs. The compactanti-rotation device produced the greatest resistance to relativerotation of the scaphoid and lunate bones in all of the traditionalcentral fixation constructs analyzed in our study. Data, which wascontinually collected at a rate of 100 samples per second, is displayedat 5 and 10 degrees of angular displacement between the scaphoid andlunate bones in Table 1 below. The particular arrangements of theexperimental groups identified in Table 1 are illustrated in FIG. 8.

TABLE 1 Experi- At 5°: N- mental Fixation mm (St At 10°: N- GroupConstruct dev) P Value mm (st dev) P value 1 3.0 mm screw 81 (80) 0.417 96 (107) 0.177 3.0 mm screw + 144 (82)  244 (167) standard staple 2 2.0mm apart K- 295 (213) 0.0872 413 (252) 0.0932 wires 2.0 mm apart K- 388(200) 525 (240) wires + standard staple 3 5.0 mm apart K- 384 (145) 0.83557 (223) 0.69 wires 5.0 mm apart K- 401 (140) 600 (171) wires +standard staple 4 3.0 mm screw 48 (22) 0.0001 77 (45) 0.0002 3.0 mmscrew + 453 (138) 656 (182) custom staple 5 2.0 mm apart K- 247 (105)0.0035 402 (189) 0.0030 wires 2.0 mm apart K- 633 (167) 879 (197)wires + custom staple 6 5.0 mm apart K- 358 (161) 0.1644 489 (212)0.1172 wires 5.0 mm apart K- 601 (449) 897 (650) wires + custom staple

When analyzed at 5°, the addition of the compact anti-rotation devicewith the 3.0 mm screw displayed approximately 9.4 times the resistanceto torque as compared with the screw alone (p-value 0.0001). Theaddition of the compact anti-rotation device to the 2 mm apart K-wireconfiguration increased resistance to torsion by approximately 2.5 timeswhen compared with the K-wire configuration alone (p-value 0.0035). Bothof these represent a substantial improvement in the amount of torquerequired to produce angular displacement at the scapholunatearticulation. In addition, the compact anti-rotation device, althoughnot statistically significant, provided approximately greater than 50%increased resistance to torsion at 5° and 10° when added to the 5.0 mmapart K-wire construct.

The compact anti-rotation device also outperformed the standard staplein each construct. The difference was most apparent and statisticallysignificant when compared with the 3.0 mm screw and the 2.0 mm apartK-wire configuration. Augmentation with the compact anti-rotation deviceversus the standard staple at 5° in the 3.0 mm screw group producedapproximately 3.1 times resistance to torque and approximately 1.1 timesgreater resistance with the compact anti-rotation device over thestandard staple in the 2.0 mm apart K-wire group (p-value 0.0003 and0.0285, respectively). Again, while not statistically significant, theaddition of the compact anti-rotation device versus the standard stapleprovided approximately greater than 60% increased resistance to torquein the 5 mm apart K-wire configuration.

When analyzing resistance to torque at the scapholunate articulationwith the current traditional central fixation constructs, the lack oftorsional stability afforded by the 3.0 mm screw becomes readilyapparent, as can be seen in Table 2 below.

TABLE 2 (Comparison of the central fixation constructs alone). Experi-At 10°: N- mental Fixation At 5°: N-mm mm (st P- Group Construct (stdev) P-value dev) value* 4a 3.0 mm screw 48 (22) 0.0005 77 (45) 0.001 5a2.0 mm apart K- 247 (105) 402 (189) wires 4a 3.0 mm screw 48 (22) 0.000477 (45) 0.0004 6a 5.0 mm apart K- 358 (161) 489 (212) wires 5a 2.0 mmapart K- 247 (105) 0.1876 402 (189) 0.4703 wires 6a 5.0 mm apart K- 358(161) 489 (212) wires

When the data is analyzed at 5°, the 3.0 mm screw provided approximately48 N-mm resistance to torsion compared to 247 N-mm for the 2.0 mm apartK-wire and 358 N-mm for the 5.0 mm apart K-wire (p-values 0.005 and0.0004, respectively). Although improved, we were not able to reachstatistical significance when analyzing the difference in resistance totorsion between the 2.0 mm apart and 5.0 mm apart K-wire constructs. Ofnote these were not matched pairs and, therefore, may require increasedpower to reach statistical significance.

The present invention may be embodied in other specific forms withoutdeparting from its spirit or essential characteristics. The describedembodiments are to be considered in all respects only as illustrativeand not restrictive. The scope of the invention is, therefore, indicatedby the appended claims rather than by the foregoing description. Allchanges that come within the meaning and range of equivalency of theclaims are to be embraced within their scope.

We claim:
 1. A method of immobilizing and securing adjacent bones andpreventing such bones from relative rotation, to facilitate healing ofthe bones or tissue or ligaments connected thereto, the methodcomprising: positioning a first bone and a second, adjacent bone atdesired locations relative to each other; inserting a first anchor of acompact anti-rotation device through a first outer surface of the firstbone and into the first bone; and inserting a second anchor of thecompact anti-rotation device through a second outer surface of thesecond bone and into the second bone.
 2. The method as recited in claim1, the compact anti-rotation device having a torsion bar extendingbetween the first anchor and the second anchor, the method furthercomprising positioning the torsion bar relative to an axis of rotationof the joint.
 3. The method as recited in claim 1, the method furthercomprising drilling a first plurality of holes into the first bone and asecond plurality of holes into the second bone.
 4. The method as recitedin claim 1, wherein inserting the second anchor of the compactanti-rotation device through a second outer surface of the second boneand into the second bone comprises inserting a second plurality ofprongs that define the second anchor into the second bone.
 5. The methodas recited in claim 1, wherein the first bone comprises a scaphoid boneand the second bone comprises a lunate bone.
 6. The method as recited inclaim 1, wherein inserting the first anchor of a compact anti-rotationdevice through a first outer surface of the first bone and into thefirst bone comprises inserting a first plurality of prongs that definethe first anchor into the first bone.
 7. The method as recited in claim6, wherein the first plurality of prongs are inserted at an anglesubstantially perpendicular to an axis of rotation of a joint defined bythe first bone and the second bone.
 8. The method as recited in claim 1,further comprising inserting at least one elongated inner connectorthrough the first bone and through the second bone, thereby fixing thedesired location of the first and second bones relative to each other.9. The method as recited in claim 8, wherein inserting the at least oneelongated inner connector through the first bone and through the secondbone comprises inserting a first K-wire and a second K-wire through thefirst and second bones.
 10. The method as recited in claim 8, whereinthe first bone comprises a scaphoid bone and the second bone comprises alunate bone and wherein inserting the at least one elongated innerconnector through the first bone and through the second bone comprisesinserting a bone screw through the scaphoid and lunate bones.
 11. Themethod as recited in claim 8, wherein the first bone comprises ascaphoid bone and the second bone comprises a lunate bone and whereininserting the at least one elongated inner connector through the firstbone and through the second bone comprises inserting a first K-wire anda second K-wire through the scaphoid and lunate bones.
 12. The method asrecited in claim 8, wherein inserting the first anchor of a compactanti-rotation device through a first outer surface of the first bone andinto the first bone comprises inserting a first plurality of prongs thatdefine the first anchor into the first bone.
 13. The method as recitedin claim 12, wherein the first plurality of prongs are inserted at anangle substantially perpendicular to an axis of rotation of a jointdefined by the first and second bones.
 14. The method as recited inclaim 8, wherein inserting the second anchor of the compactanti-rotation device through a second outer surface of the second boneand into the second bone comprises inserting a second plurality ofprongs that define the second anchor into the lunate bone.
 15. Themethod as recited in claim 8, wherein inserting the at least oneelongated inner connector through the first bone and through the secondbone comprises inserting a bone screw through the first and secondbones.
 16. The method as recited in claim 15, wherein inserting thefirst anchor of a compact anti-rotation device through a first outersurface of the first bone and into the first bone comprises inserting afirst plurality of prongs that define the first anchor into the firstbone.
 17. The method as recited in claim 16, wherein the first pluralityof prongs are inserted at an angle substantially perpendicular to anaxis of rotation of a joint defined by the first and second bones. 18.The method as recited in claim 16, wherein inserting the second anchorof the compact anti-rotation device through a second outer surface ofthe second bone and into the second bone comprises inserting a secondplurality of prongs that define the second anchor into the second bone.19. A method of immobilizing and securing adjacent bones and preventingsuch bones from relative rotation, to facilitate healing of the bones ortissue or ligaments connected thereto, the method comprising:positioning a first bone and a second, adjacent bone at desiredlocations relative to each other; drilling a first plurality of holesinto the first bone and a second plurality of holes into the secondbone; inserting a first anchor of a compact anti-rotation device througha first outer surface of the first bone and into the first bone, thefirst anchor having a first plurality of prongs; and inserting a secondanchor of the compact anti-rotation device through a second outersurface of the second bone and into the second bone, the second anchorhaving a second plurality of prongs, the compact anti-rotation devicehaving a torsion bar extending between the first anchor and the secondanchor.
 20. A method of immobilizing and securing adjacent bones andpreventing such bones from relative rotation, to facilitate healing ofthe bones or tissue or ligaments connected thereto, the methodcomprising: positioning a first bone and a second, adjacent bone atdesired locations relative to each other to form a joint; drilling afirst plurality of holes into the first bone and a second plurality ofholes into the second bone; inserting a first anchor of a compactanti-rotation device through a first outer surface of the first bone andinto the first bone, the first anchor having a first plurality ofprongs, the compact anti-rotation device having a torsion bar extendingbetween the first anchor and a second anchor; positioning the torsionbar relative to an axis of rotation of the joint; and inserting thesecond anchor of the compact anti-rotation device through a second outersurface of the second bone and into the second bone, the second anchorhaving a second plurality of prongs.